1. Field of the Invention
The present invention relates to bearing technology and more particularly, to a roller bearing, which has low sliding friction.
2. Description of the Related Art
Referring to FIG. 1, a conventional roller bearing 10 is known comprising an inner race 11, an outer race 12, and a plurality of rollers 13 rotatably accommodated between the inner race 11 and the outer race 12. The inner race 11 and the outer race 12 each define therein two raceway faces 112;122 abutted at right angles. Each roller 13 has the cylindrical surface 132 thereof rotatably kept in contact with one raceway face 112 of the inner race 11 and one raceway face 122 of the outer race 12, allowing the inner race 11 and the outer race 12 to be fastened together and rotatable relative to each other. Because rolling contact causes less friction resistance, the inner race 11 and the outer race 12 can be smoothly rotated relative to each other, and a less amount of torque is required to rotate the inner race 11 and the outer race 12.
Among the commercial roller bearings, the length of the rollers 13 is approximately equal to the outer diameter of the rollers 13, and also approximately equal to the width of the raceway faces 112;122. Thus, the cylindrical surface 132 of each roller 13 is almost fully kept in contact with the raceway faces 112;122. Because the tangential velocity at different portions of the raceway faces is different, sliding between the rollers 13 and the raceway faces 112;122 causes a rise in friction resistance.
In other words, the large contact length between the rollers and raceway faces of the conventional roller bearings leads to a large friction resistance. If these roller bearings are used in a high speed device, they can be damaged easily due to a rapid rise in temperature. Therefore, improvement in this regard is desired.